Fuel injection pump plunger



July 25, 1950 Mac oNALD 2,516,521

FUEL INJECTION PUMP PLUNGER Filed March 26, 1949 2 Sheets-Sheet 1 a l I v INVENTOR.

-ROM/LAND MACDQNALD July 25, 1950 R. M DONALD 2,516,521

FUEL INJECTION PUMP PLUNGER Filed March 26, 1949 2 Sheets-Sheet 2 Tag. 5 3

a 4 g T i 6 INVENTOR. 7 ROWLAND MACDONALD ATTORN EY Paiented duly 25, that caisson I FUEL INJECTION P PLUNGER Rowland Macdonald, Lonow, as-

American Bosch Corporation, Springa corporation of New York Application March 2c, 1949, Serial No. asses I 3 Claims. i 1 r This invention relates to fuel injection apparatus and to a new and improved process of making the same.

An object of the invention is to provide a new and improved plunger for fuel injection apparatus and a process of making the same.

Another object of the invention is to provide a new and improved plunger for fuel injection apparatus and a new and-improved process for 1 accurately forming a lead thereon.

Another object of the invention is to provide a new and improved process of forming metering leads on plungers of fuel injection apparatus which provides a lead of desired accuracy and which is considerably simpler and more economical than previous processes employed for 9 P p Other objects and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawings and it will be understood that modifications may be made in the details of construction and steps of the process without departing from the scopegof the invention as expressed in the accompanying claims.

Referring to the drawings: I

Fig. l is a side view'of a plunger showing a step in the process of manufacture thereof;

rig.2isaviewsimilartol 'ig.1butshowinga completed plunger;

Fig. 3 is a fragmentary view-oi the plunger shown in Fig. 1 but on an enlarged scale;

Fig. 4 is a fragmentary view of the construction shown in Fig. 2 but on an enlarged scale;

Fig. 5 is a development of the end of the plung- 35 er shown in Fig. 1 on which the metering lead is formed;

Fig. 6 is generally similar to Fig. 5 but shows the construction of the plunger of Fig. 2; and

Fig. 7 is a view illustrating a step in the process of' forming the metering lead on the plunger In the manufacture of plungers for fuel injection apparatus it is that the metering leads or threads which are usually in the form of a helix must be accurately formed in 46 views, theplunger shown in Fig. 1 comprises the body portion i, flange 2 and'head I.

The plunger head' 3 has the vertical slot 4 formed therein and also is provided with the helix or helical shoulder 5.

The helix or helical lead 5, which is of spiral or helical form and is generally similar to a stretched out screw thread, and the lead of the helix has a definite bearing on the load range of the engine and the control rack travel required to deliver a certain amount of fuel for a certain load. For example, with a plunger having a steep helix lead, it will deliver for the same control rack movement, a much greater fuel delivery that'would be possible with the use of a plunger having a less steep helix lead. In actual engine application an engine requirin a relatively narrow range of load control employs comparatively less steep leads on the plunger helix and if a greater lead range is desirable, plungers with a steep helix lead are used.

The direction in which the helix runs must be either left-hand running or right-hand running and in the drawingsa left-hand helix is shown by way of illustration only.

If desired, an upper helix or lead t may be employed for variable end of injection as well as the variable beginning of injection given by the helix 5.

It will be seen from the above that in order that the plunger may beso constructed as to give the desired injection characteristics to the pump, that the helix or lead 5 must be very accurately formed on the head 3 of the plunger I.

In the prior constructions where this helix or lead has consisted only of the shoulder 1 shown in Fig. 3, this has been diflicult as well as expensive because of the difllculty encountered in accurately grinding the shoulder I.

In the plunger construction embodying the present invention as shown in Figs. 2, 4. 6 and 7, the helix or lead is formed by accurately grinding or beveliing the outer edge 8 of the helix or lead which may be done with a grinding wheel as shown in Fig. '7 and which eliminates the necessity of accurately grinding the entire shoulder I on the helix or lead I thereby considerably simplifying and reducing the cost of formingaccurate helices oi metering leads on plungers for fuel injection equipment.

In the formation of the bevelled helix or metering lead 8 the use of a grinding wheel is preferable although not essential as it allows the forming of an accurate edge on a cylindrical sur- 3 faeswhileusingaslargeagrindingwheelas possible for high surface speed.

Theupperhellxteouldalsobesoformedif desired In forming the bevelled lead I. the plunger I may be supported by centering means ll so eonsn-ueted as to allow the movin of the plunger and wheel relative to each other and preferably the plunger I is helically advanced and retracted relative to the grinding wheel I whereby said wheel will form said bevelled edge on the shoulc der I to thereby produce the accurate lead I as previously described.

From the foregoing it will be seen that I have provided a simple, eillcient, accurate andecov 4 plunger for use in fuel injection equipment. said plunger having a head portion and a metering leadinsaidheadportiomsaidleadcomprising a shoulder having a bevelled edge throughout at leastaportion thereof.

3. In a device of the character described. a plunger for use in fuel injection equipment, said plunger having a head portion and a helical metering lead in said head portion, said helical lead comprising a shoulder and said helical lead having a bevelled edge throughout at least a portion thereof.

ROWLAND MACDONALD.

REFERENCES CITED The following references are of record in the die of this patent:

UNITED STATES PATENTS Number Name Date 1,847,718 Herr Mar. 1, 1932 2,187,732 De Juhass Jan. 23, 1940 2,382,000 Bremser Aug. 14, 1945 2,384,011 Bremser Sept. 4, 1945 

